Method of producing prolamine filaments



patented Aug. 9 1949 METHOD" OF PRTO DUCING PROLAM IN E FILAMENTS Glarence B.- .Croston,,Peoria,. and Cyri LD. Evans, Peoria Heights, 111., assignors to the United States of. America as represented by the Secretary ofl igriculture No Drawingazipplication o'ctober 5,;1 948,'. Seriat No. 52,970

(Granted underthe act of March 3, 1883, as

amended April 30, 1928-; 37-0 0; G. "7 57?) This applicationis made. under the act of March 3, 1883, as amended by the act of April 30; I928; and the invention" hereindeseribedi if patented in country; may be manufactured and used byor' fertile Government of the United States of America for governmental purposes throughout the World without the payment to us of any royalty thereon.

Thisinveiition relates to'the' roduction of pro teinfilam'entsg and hasaimong its obiectsthem ode ification of aprolamin'e, such as z'ein, bye-combined series of steps; before, during, and after spinning to produce fibers having propertieshere tofore unobtainable. Other objects wili be. an parent from the description or the-.inventioni.

Although theproeess of thisiinyeritionis appli cable to the-general class of prolamines-g .zeinisthe only IiiFdlSAiliIl vrl iic'h has attained: 'substan tial industrial importance-3 The .ini/en-tion will: therefore be described with particular regard to the piroduetio lof filaments from'zein.

Zein is an alcohol-soluble protein convention ally extractedziromncorn gluten residue; a product in" the Wet milling ofcorn for the. production of corn starch. Zeinis producedby extraction of. this crudepgiutenwith alower alcohol; such as ethanol or iso'propyl alcohol, precipitation and drying. Zeinprepared: by thisor other known methods may be used in the process of the invention. It is a relatively inexpensive protein which has beenfound to-havemany valuable characteristics when-spun into fibers. However zeinfibers or filaments have a tendency to blush and shrink when brought into contact with water. This characteristic is a serious limitation upon the useof zein fibers, especially since it has been found that the coarser fibers of the bristle type are particularly adaptable for use in brushes.

In application S'erialNo. 528,479; of C. D. Evans; C. W. Ofelt, and AK. Smith, filedM'archZB', $944, a process for producing fib'ersi's' described" which includes spinning an aqueous alkaline dispersion of zein', the dispersion containing" an aldehyde or an alde'hyd'eeyieldihg' agent. Fibers produced by this process, although possessing superior strength and other characteristics, ha'vea tendency to turn white or blush and shrink on contact with water. I

Various heat treatments have been applied heretoforein thepreparation =o'r finishing of zein products; United StatesPatentNmfiAOEhZB; issued to C; D; Eyans;..a method: is describedlton preventing the blushing of zero. reaet ing: zeiniin a :solutionior volatile: solvent withc-an aldehyde aii temnerature'sich50? and. over; and suio's'equentlyhahing"theiciaSt flhriat-IBO G. Films or' hodies prepared? in: this iii-12111181 haveaconsid erable resistance to blushing! fniflnitedlstates Patent Nee 2156;929; issued to L4 0. Swalleni, a method-is described forxproducin'g filaments by spinning volatile solvent solutions or zein which contain an aldehyde;:inttran aldehyde-containingz loath. and subsequently heating: the filament to temperatures belowrooca to-eva ioratewaterand promote reaetionbetween aldehyde and zeiii. As=- W-iil be Seen tram: the ensuing description; the temperatures employed in niese -prior' patented process as are considerably lowerwthan mos l 'e quired in the baking step df this inventionand are insufiikiie'r'it t'd tin-part appreciable watezf resistaiiceto the-zeih fibers.-

Our process is essentially one forzinodiiyine the proiamiiie by aldehyde treatinenit steps and bye-heat treatment or baking siege. Thee/sent mechanism of modification isnot knowiabutzwe believe it is ibrthe m'ostpart a pro-gressiveialtera tibriof the protein through a series ofisucc'essiiie stagesof chemicar reaction between the: pix lei-mine and the aldehyde. Threeess'e'fitial 1:? 'di ficatiorr steps are involred whi'cn -maybesimmer ated briefly as follows 1. Aldehyde modification of the oral-amine an alkalihed'i'spersiozrbefore spinning;-

2. Spi'iinin'g= the fibers into an acid b'atr i th spinnin being associated with a mild aidenyde cure.

3. A thorough balding 'tre'atmeri t.- Allof thesestepsinust kie fiollowedtd achieve: pro: diitjtioriofthe" fibers ossessing: the: improved characteristies'.

The first step, which may be termedazpreiir'niinary modification of 'the zein while in: amailtaline dispersion; is cariieli out within-apH range or 1110 terms; aldehyde is piefraifi-iy tomaid'ehyue and the amount used may from '/g to E0 percent 'based on the" weihht of. the: The reaction is completed iii about 2 to edayseatapproximately room temperatures Instead of formaldehyde, other aldehydesfisuclizias' acetaldee hyue, propibrialdehydeg benzaldehydez and flir- 3 fural, may be used. Furthermore, aldehydeyielding compounds, such as trioxymethylene and hexamethylenetetramine, may be used. The amount of aldehyde introdued into the fiber may vary from 0.3 percent to 4.0 percent, based on the weight of the zein.

The second step which is similar to the precure of older zein modification methods may be carried out in two separate stages. When the fibers are spun, they may be run directly into an acid bath where the protein is coagulated, then drawn from this bath into another bath containing acid and the aldehyde. The second bath contains about 10 percent aldehyde, a small amount (usually about 1 percent) of a. catalyst, such as ammonium sulfate, ammonium phosphate, ammonium chloride, and the like; and about 5 percent of an alkali salt, such as sodium sulfate, may be added to prevent plastering together of the filaments. Although it is not necessary, it is pref erable that the negative radical of the ammonium and sodium salts correspond to the acid employed in the coagulating bath. An unnecessary mixture of acid radicals is thus avoided. For reasons of convenience the acid used should correspond in both acid baths. Any of the usual coagulant acids may be used, such as sulfuric, phosphoric, acetic, hydrochloric, and the like.

. The pH of both baths ranges from about 1 to 3. The time of treatment ranges from 15 to 30 minutes at a temperature of 30 to 55 C. During this treatment about 1 percent aldehyde is introduced into the fibers.

The two acid baths may be combined to make the second step a single operation. In other words, the acid bath into which the fibers are spun, having a pH of between 1 and 3, may also contain percent by weight of aldehyde, the ammonium salt catalyst, and the alkali salt. This bath is then held at a temperature between 30 to 55 0., and the fibers kept immersed for to minutes. The fibers drawn from the acid formaldehyde bath usually contain over 1 percent combined aldehyde.

- As in the previous step, other aldehydes or aldehyde-yielding agents may be used, although formaldehyde is preferred.

After washing, stretching from 50 to 300 percent, and drying the filaments from the acid formaldehyde step, they are given a baking treatment for about from 10 to 60 minutes. The preferred conditions for baking are 160 to 170 C. for about 15 minutes. Lower temperatures require longer baking, and the lowest practical temperature is about 140 C. For example, although the reaction at 140 C. is of considerable benefit to the fibers, treatment at this temperature for 60 minutes is not equivalent in beneficial results to a 15-minute treatment at 160 C. At temperatures of 180 C. or above the filaments begin to darken and the strength begins to drop off due to thermal deterioration of the fiber. A certain amount of aldehyde is lost from the fibers during this treatment. The range of formaldehyde in the final baked filament is about 0.5 to 2.5 percent.

The exact chemical mechanism of the steps of this invention is not known. It is believed that the aldehyde may have been introduced during the two preceding steps as chemically combined aldehyde, either by direct chemical union or by the formation of addition complexes. It is entirely possible that prior to the baking step the aldehyde is present in both forms.

The process is a much quicker and simpler finis es procedure for producing prolamine fibers than any known previously. The fibers produced are higher quality and capaole of more extensive uses than previous proiamine nbers. They have greatly improved water resistance and the shrinkage is reduced lower than ever before. In spite of the fairly drast1c conditions for baking, it is remarkable that the strength is not materially decreased nor the color of the dry Iiber materially changed.

Omission oi the formaldehyde treatment in the initial step results in nbers which blush easily and do not have the greatly improved shrinkage characteristics. This 15 illustrated by the data of Table LLI, which is set 101'131'1 below. The second step or spinning the nbers into an acid bath, the spinning being associated with the mild aldehyde cure, is, of course, necessary to obtain a satisi'actory fiber. Fibers without the acid coagulation or the mild cure would have no appreciable strength and little elasticity. The baking step is, of course, essential belore appreciable water resistance or decreased shrinkage is attainable.

The following examples illustrate the invention:

EXAMPLE I A sample of commercial alcohol-extracted and umnodified zein was used in preparation of filaments. The procedure was as follows:

FIRST STEP Nine hundred g. of zein was mixed with 4800 ml. of cold water until a smooth slurry was obtained. To this slurry was added g. of urea followed by the slow addition of 1000 ml. of .lN sodium hydroxide from a separatory funnel. The function of the urea is a denaturing agent to accelerate aging of the protein. Thirty ml. of formalin (40 percent formaldehyde, equal to 1.3% percent formaldehyde based on the weight of the zein) was mixed with 200 ml. of .4N sodium hydroxide and added through the separatory funnel. The reaction mixture was stirred and mixed with a high-speed stirrer, stirring being continued for one hour after addition of all ingredients.

A low viscosity dispersion resulted which was filtered through a fine filter. It was then stored under controlled conditions (22 C. for 3 days). During this period, deaeration, ageing, reaction with the formaldehyde and the development of spinning viscosity are all accomplished.

SECOND STEP Filaments were spun from the above-described solution into an acid bath containing 800 ml. of acetic acid and 12 l. of water. A 40-hole, 0.040 diameter jet was used. The filaments were withdrawn from this coagulation bath, washed, and stretched before being dropped loose into the mild formaldehyde curing bath. Curing may be accomplished by two methods, namely, a batch or slow cure and a continuous or fast cure. Both types of cures were carried out on separate samples of filaments in this example.

In the batch cure the tow of filaments was given a slight stretch before being dropped loose into a large curing tank. The curing bath was made up in the following proportions: 12 l. of water, 600 ml. of 40 percent formalin and 40 g. of ammonium chloride. The bath had a pH of about 2.0. The filaments, when dropped into the bath, formed a sort of cake in the tank. For the cure, the bath containing the filaments was allowed to stand for 2'7 days at room temperature. At the end of the seventeenth day the formaldehyde content of the filaments was found to be 2.30 percent. At the end of the twenty-seventh day the formaldehyde content was 2.82 percent.

The continuous or fast method of curing is as follows: The washed tow of filaments was stretched slightly and dropped loose into a curing bath consisting of percent formaldehyde, 1 percent ammonium sulfate, and 5 percent sodium sulfate. The pH of the bath was about 2.5. Two different runs were made, the first being a 30-minute cure at 33 C.; the second being a 30-minute cure at 50 C. Formaldehyde content of the filaments in the 33 C. cure was found to be 1.87 percent. In the 50 C. cure it was found to be 1.73. After curing by either the slow or fast method the filaments were withdrawn, washed, stretched, and dried continuously in a hot air countercurrent system.

THIRD STEP The following Table I illustrates the change in strength of the zein fibers as the baking temperatures are increased. The term raw fiber refers to the unbaked fiber. The terms dry strengt and knot strength refer to the load in grams for individual filaments of substantially equal diameter at 70 F. and 65 percent relative humidity. The knot strength was determined after tying an overhand knot in the filament. It will be noted that the strength of the raw zein fibers is slightly less than the baked fiber at temperatures below about 160 C. As the baking temperature is increased, the strength begins to drop slowly until at 180 C. the fiber begins to be adversely affected. Between these two temperatures, both the dry strength and the knot strength, although slightly decreased, are not appreciably below the strength of the raw fiber. As would be expected, temperatures above 180 C. begin to cause deterioration of the fiber.

Table I also shows the effect of baking temperatures upon the shrinkage of zein fibers. In every case the fibers had been baked for minutes and the shrinkage determined by an 18-hour treatment of the fibers in water at room temperature. As may be noted, the shrinkage, over percent in the unbaked fiber, is gradually reduced as the temperature of baking is increased until a minimum is reached at about 160 C., at which temperature the shrinkage remains below 7 percent as the baking temperature is increased.

The effect of baking on strength and shrinkage,

using the batch and continuous cure is shown in Table II, following:

We have discovered that beneficial effects of our invention are more pronounced in processes for making coarse or bristle type fibers. Nevertheless, the finer textile fibers show considerable improvement. The following table illustrates the effect of formaldehyde in the dispersion, i. e.,

in the initial or preliminary modification of fibers prepared by procedure similar to that of Example I. In the initial step the formaldehyde treatment was omitted for control fibers for the purpose of comparing the resulting shrinkage. In every case the heating step was carried out by baking at 167 C. for 15 minutes. The shrinkage in every case was determined by an 18-hour treatment of the fibers in water at room temperature.

Having thus described our invention, what we claim is:

1. A process for the production of a prolamine filament comprising reacting an aqueous alkaline dispersion of a prolamine with an amount of aldehyde equal to from to 10 percent based on the weight of the prolamine, spinning the dispersion into an acid bath to coagulate the prolamine, curing the spun filament in an acidaldehyde bath of pH from 1 to 3 at a temperature of from 30 C. to 55 C., removing the filament, Washing, stretching, and dryin it, and then heating the dried filament at a temperature between C. and C.

2. The process of claim 1 wherein the prolamine is zein.

3. The process of claim 1 wherein the aldehyde is formaldehyde.

CLARENCE B. CROSTON. CYRIL D. EVANS.

No references cited. 

